Musnad Ahmad 3:26

'Abdullah narrated to us, Muhammad ibn Abi Bakr al-Muqaddami narrated to us, Abu Ma'shar—meaning al-Bara', and his name is Yusuf ibn Yazid—narrated to me, Ibn Harmalah narrated to us, from Sa'id ibn al-Musayyib, who said: 'Uthman went on Hajj. When he was on some part of the road, it was reported to 'Ali that 'Uthman had forbidden his companions from performing *Tamattu'* (combining 'Umrah and Hajj). 'Ali said to his companions: "When he departs, then depart." So 'Ali and his companions entered into the state of *Ihram* for 'Umrah, and 'Uthman did not speak to them. 'Ali said: "Was I not informed that you forbade *Tamattu'*? Did the Messenger of Allah, peace and blessings of Allah be upon him, not perform *Tamattu'*?" He said: So I do not know what 'Uthman, may Allah be pleased with him, answered him.